Sr-doped Li4Ti5O12 composites are prepared by a solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and transmission electron microscopy. Their electrochemical properties as the anode material of lithium ion batteries are investigated by galvanostatic charge and discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that Sr2+ doping increases the lattice parameter, reduces the particle size, decreases the charge transfer resistance, and significantly enhances the rate capability of Li4Ti5O12. The Sr-doped Li4Ti5O12 exhibits a specific discharge capacity of about 1.62 times that of pristine Li4Ti5O12 at 5 C charge/discharge rate. Sr doping introduces a small amount of SrLi2Ti6O14 to the composites, which also makes a contribution to the specific capacity of Li4Ti5O12 at low charge/discharge potentials. (C) 2012 Elsevier B.V. All rights reserved.